Thread tension device for sewing machines



July 25, 1961 E. J. HERBST THREAD TENSION DEVICE FOR SEWING MACHINES Filed Sept. 9, 1959 3 eets-Sheet 1 EDWARD J. Hsnasr TTORNEY R 4 w W m I W 3 4 2 2 M %f\ w 2 llllll 1| F m lnu w km w M n, w 2% .m w F p 2 .m F

WITNESS THREAD TENSION DEVICE FOR SEWING MACHINES Filed Sept. 9, 1959 E. J. HERBST July 25, 1961 3 Sheets-Sheet 2 H m m5 H Ma 0 m w E BY WITNESS Fi .4. fla W 5 9 W ATTORNEY July 25, 1961 E. J. HERBST THREAD TENSION DEVICE FOR SEWING MACHINES iled Sept. 9, 1959 a sneets W ENToR. EDWARD HERBsr TTORNE United States Patent 2,993,456 THREAD TENSION DEVICE FORSEWING MACHINES Edward J. Her-last, South Piainfield, N.J., assignor to The Singer Manufacturing Company, Elizabeth, N.J., a

corporation of New Jersey Filed Sept. 9, 1959, Ser. No. 839,029 1 Claim. (Cl. 112254) This application is a continuation-in-part of my prior oopending application Serial No. 797,183, filed March 4, 1 959, which application is now abandoned.

The present invention relates to sewing machines, and more particularly to a thread tension device for sewing machines.

The object of this invention is to provide an improved thread tension device for sewing machines, which device, while being positioned in the front wall of the machine head, is constructed such that it will not interfere with visibility at the point of stitch formation, and which includes a tension release mechanism adapted to be actuated by the presser lifter lever in the usual manner from the rear of the machine head. It is also an object of this invention to provide a needle thread tension device of the type disclosed in applicants prior Patent No. 2,843,336, July 15, 1958, in which the cleaning or replacement of the tension discs has been facilitated. This end has been accomplished in accordance with the present invention by making the tension discs readily removable from the front of the machine. Further objects of this invention are to provide a thread tension device that is economical in that it is composed of a minimum number of parts, each of which is inexpensive to manufacture, is recessed into the head of the machine to reduce interference with manipulation of the work and visibility, to reduce the possibility of damage and to improve the appearance of the machine, is dependable and eflicient particularly in that it will efiectively hold a desired setting and will return to that setting after actuation of the tension release mechanism and, therefore, will produce a uniform thread tension, and is designed to be actuated by a tension release mechanism that can be conveniently accommodated in the head of the sewing machine.

Having inmind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, constructions and advantages of it when read in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary elevational view of the head portion of a sewing machine embodying the present invention.

FIG. 2 is a vertical transverse sectional view taken substantially on the line 22 of FIG. 1.

FIG. 3 is a fragmentary sectional view taken substantially on the line 33 of FIG. 2.

FIG. 4 is an exploded perspective view of the tension device shown in FIG. 1.

FIG. 5 is a vertical sectional view similar to FIG. 2, but illustrating a modification of the invention.

FIG. 6 is an exploded perspective view similar to FIG. 4 of the parts of the modification of the tension device illustrated in FIG. 5.

With reference to the drawings, there is illustrated a fragmentary portion of the frame of a sewing machine, or more particularly of the head 1 of a sewing machine. In the upper portion of the head 1, there is a boss 2 in which is formed a hole 3 extending inwardly from the front wall of the head. A rod 4 is arranged centrally of ice the hole 3 and is journaled in a bore 5 provided in an end wall 6 that defines the bottom of the hole 3. To hold the rod 4 against endwise movement and to provide a frictional resistance to turning thereof so that it will hold a desired setting, the rod 4 is provided with a shoulder 7 for engaging the inner face of the end wall 6 and, within the head 1, is surrounded by a coil spring 8 that acts between the outer face of the end wall 6 and the head of a screw 9 threaded into the end of the rod. The rod 4 is thus biased inwardly to hold the shoulder 7 in engagement with the face of the end wall 6.

On the free end of the rod 4 exteriorly of the machine head 1, there is mounted a head 10 that serves as a knob or finger piece for efiecting manual turning of the rod. The head iii is secured on the rod 4 by a set screw 11. inwardly of the head 14), there is mounted on the rod 4 a sleeve 12 having a flange at the end adjacent to the head 11 and defining a shoulder or abutment 13. Sandwiched between the head 1% and the end of the sleeve 12 is a dished plate 14. The plate 14 has a central aperture 15 for mounting it on the rod 4 and a pin 16 that is re ceived within a bore 17 in the head it} for keying the plate to the head for turning. A thread guard 18 is mounted on the rod 4 inwardly of the plate 14 and has an arm 19 adapted to enter a hole in the head 1 to secure the guard against turning. The shoulder 13 serves as a stop for limited outward movement of the thread guard 18 on the sleeve 12. For limiting turning of the rod 4 to one revolution, the thread guard 18 has a lug 2% that is positioned in the path of a lug 21 on the plate 14.

Within the hole 3, the rod 4 is formed with a threaded portion 22 on which an adjusting nut 23 is screwed. The adjusting nut 23 is formed with a pair of diametrically arranged, laterally extending lugs 24 that are received within longitudinally extending slots 25 formed in the cylindrical side wall 26 of a barrel 27. The barrel 27 surrounds the adjusting nut 23 and is mounted in the hole 3 for endwise sliding. The sleeve 12 is mounted on the rod 4 outwardly of the adjusting nut 23 and at its inner ends abuts against a shoulder 23 at the end of the threaded portion 22. Mounted on the sleeve 12 for endwise sliding is a slide member 29 in the form of a sleeve having a lateral flange 39. A compression spring 31 is coiled about the rod 4 between the adjusting nut 23 and the sleeve 29 and acts against the adjusting nut 23 to bias the sleeve v29 outwardly. Between the outer end of the sleeve 29 and the thread guard 18, there is mounted on the rod 4 a pair of opposed tension discs 32 between which a thread lead is adapted to be placed for the purpose of placing a tension upon the thread as it is pulled through the tension device. A bias is placed on the tension discs 32 by the spring 3 1 wmch, acting against the adjusting nut 23 and through the sleeve 29, biases the discs 32 outwardly against the thread guard 18 and, in turn, against the shoulder 13 on the sleeve 12, the indicia plate 14 and the head 16.

The barrel 27 is held against turning by a vertically arranged tension releasing lever 33 disposed at the front of the head :1 directly beneath the tension device and pivotally mounted intermediate its ends in the head 1 on an axis perpendicular to the axis of the rod 4 by a pivot screw '34. The tension releasing lever 33 has an upwardly extending arm 35, the upper end of which enters into a hole 36 in the side wall 26 of the barrel 27. Thus, when the rod 4 is'turned by grasping the head 16, the adjusting nut 23, which is held against turning by the engagement of the lugs 24 Withth'e slots 25, is caused to move axially of the 'rodl4 to vary the compression of the spring 31 and thereby to adjust the tension placed upon the thread being drawn between the discs 32.

To release the tension on the thread, the bias is removedfrom the discs 32 by retracting the sleeve 29 from 3 engagement with the discs 32 against the action of the spring 31. This is accomplished by the barrel 27 which is provided with an inturned flange 37 that extends inwardly toward the sleeve 29 and terminates in a free edge 38 adjacent to the periphery of the sleeve and outwardly of the flange 30. Thus, when the barrel 27 is retracted into the hole 3, the flange 37 engages the flange 30 and forces the sleeve 29 inwardly away from the tension discs 32. To retract the barrel 27, the tension releasing lever 33 has a depending lever arm 39 that is engaged by one arm 40 of a bell crank lever 41 pivotally mounted in the head 1 on an axis parallel to the pivot axis of the lever 33 by a pivot screw 42 and having a second lever arm 43 that is adapted to be engaged by a pin 44 on the presser lifter lever 45. In the usual manner, the presser lifter lever 45 is pivotally mounted at the rear of the head 1 on a pin 46 and operates through a slot 47 in the rear wall of the head 1 and has a cam surface 43 adapted to engage a collar 49 on the presser bar 50 for raising and lowering the presser bar. The barrel 27 is biased into its inoperative position by a spring 51 arranged between the frame and the end of the lever arm 39, the inoperative position being determined by a stop lug 52 on the frame and adapted to be engaged by the end of the lever arm 43. The barrel 27 is thus not only held against turning by the lever arm 35, but is also positioned endwise by it. By positively moving the barrel 27 to its inoperative position, it is insured that the sleeve 29 is completely released to restore the tension.

in the initial assembly of the tension device, the rod 4 with the adjusting nut 23 mounted thereon is inserted into the hole 3 and into the bore from the front of the machine until the shoulder 7 abuts against the wall 6. The spring 8 is then placed on the end of the rod 4 and the screw 9 is threaded onto the rod. The rod 4 is thus held endwise in place, the bore 5 providing a bearing for the rod and the spring 8 biasing the shoulder 7 against the wall 6 at the end of the bore 5 to prevent withdrawal of the rod and rattling of the parts while permitting the rod 4 to turn and to be held frictionally in the desired position. The spring 31 is then inserted after which the sleeve 29 and barrel 27 are placed in position and secured by fastening the lever 33 in place by the pivot screw 34. The sleeve 12 with the tension discs 32 and the guard 18 thereon can then be inserted. Finally, after the dished plate 14 is placed on the rod 4, the head is placed on the rod 4 and positioned endwise therein by engagement with the end of the sleeve 12 which in turn engages the shoulder 28, and it is secured on the end of the rod 4 by the set screw 11 to lock the assembly. For adjusting the range of the tension, the set screw 11 is loosened and the head 10 is turned relatively to the rod 4. The plate 14, being secured to the head 10 by the pin 16 and hole 17, turns with the head 10. Thus the location of the lug 21 varies to effect an adjustment of the minimum and maximum settings of the tension.

When once assembled, the tension discs 32 can be removed simply by loosening the set screw 11 and removing the head 10. The discs 32, together with the plates 14 and 18 and the sleeve 12, can be slid off the rod 4 from the front of the machine. The rod '4 itself can also be removed bybacking ofi the screw 9 and sliding it forward through the sleeve 29 after it has been turned free of the adjusting nut 23. When the rod 4 is removed, the re- ,rnaining elements are held in the machine substantially in assembled relationship. The barrel 27 is held by the lever 33. Within the barrel 27, the spring 31 has expanded to hold the adjusting nut 23 against the face of the wall 6 and the sleeve 29 against the flange 37 of the barrel. The rod 4 can then be reinserted through the sleeve 29, adjusting nut 23 and into the bore 5.

The construction in accordance with applicants above noted prior patent has the advantage that it provides, in

'arecessed tens-ion device, a construction which will dependably return to its original setting after actuation of the tension release mechanism. A recessed thread tension device has the advantage that, being recessed in the head, it constitutes a minimum obstruction to manipulation of the work and in the operators line of vision to the point of stitch formation, is less likely to be damaged, and improves the appearance of the machine. The further advantages of the tension device disclosed and claimed in applicants prior patent are that it is economical to manufacture and to assemble in the machine, is simple and easy to adjust, is dependable and durable and provides a uniform tension on the thread.

The object of this invention is to eflect additional improvements over the prior construction while retaining all the advantages of that construction. More particularly, in accordance with this invention, the tension device has been relocated so that it will not obstruct the line of vision as was the case when located at the lower portion of the head, and the tension device has been modified so that the tension discs can be conveniently removed from the front of the machine.

There are many considerations involved in the location of the tension device. The location of the various other elements of the thread system, such as the take-up mechanism and the check spring, must be such as to accommodate the relocated tension device.

In the illustrated machine, to obtain the desired thread path while securing a more favorable location of the tension device, the check spring has been separated from the tension. As shown, the check spring, which is generally indicated at 53, is located near the bottom of the head 1. To accommodate the check spring, the head 1 is provided with a boss 54 having a hole in which there is mounted the check spring arbor 55 which is secured in angularly adjusted position by a set screw 56. The arbor 55 is provided with an enlarged intermediate portion 57 having a series of endwise extending grooves 58 in the periphery thereof. The check spring 59 is coiled about the portion 57 and has the one end anchored in a selected one of the grooves 58. Secured on the free end of the arbor 55 by a screw 60 is a. spacer 61 having a threading groove 62 and a guard plate 63 having the usual thread guide and stop for the free end 64 of the check spring. With this arrangement of the check spring 53, there is obtained a favorable check spring action and at the same time, there is obtained a favorable lead for the needle thread relatively to the take-up, which is indicated at 65.

Another consideration eifecting the location of the tension device is the release of the tension that must be effected when the work is to be withdrawn from the machine. The tension release has heretofore been coupled to the presser lifter lever for the reason that the release of the tension is normally desired only at the time the presser is lifted and the presser lifter lever affords a simple and effective actuating element for the tension release. The presser lifter lever is necessarily located at the lower rear portion of the head and the operative connections from it to the tension device must be accommodated within the head without interfering with the other elements in the head such as the needle bar, needle bar crank, and take-up.

In accordance with the present invention, there has been provided a tension device that is located and operatively connected to the tension release mechanism that will satisfy all of these requirements. The tension device is located at the top of the head where it is not in the operator's line of vision. By separating the check spring from the tension device, the thread handling requirements are satisfied. The disclosed tension release mechanism is adapted ,to be actuated by the presser lifter lever and is operatively connected to the relocated tension device to effect release of the tension by connections that do not interfere with the other elements in the head.

In FIGS. 5 and 6, there is illustrated a modificationl of the invention. The embodiment of the invention illustrated in FIGS. 5 and 6 is the same as that of FIGS. 1-4, except that the sleeve 29 has been eliminated, the head and the plate 14 are formed as a single piece, and the means for holding the rod 4 against endwise movement, i.e., the spring 8 and screw 9 have been modified. Those parts of the tension device illustrated in FIGS. 5 and 6 that are the same as the corresponding parts illustrated in FIGS. 1-4 have been identified by the same reference numerals.

With reference to FIGS. 5 and 6, there is provided a boss 2a in the head 1, which boss is enlarged relatively to the boss 2 and is provided with a slot 66 that exposes a portion of the rod 4a at a point adjacent to the inner end thereof. In the portion of the rod 4a exposed by the slot 66, there is provided a peripheral groove 67. The slot 66 also accommodates a leaf spring '8a that is secured to the top of the boss 2a by a screw 9a extending through an elongated slot 68 in the spring 80. The leaf spring 8a includes a depending arm having a slot 69 in the end thereof that is less in width than the diameter of the rod 4a adjacent to the groove 67 but greater than the diameter of the rod 4a at the base of the groove 67. The slot 69 receives the rod 4a with the bifurcated ends of the leaf spring 8a formed by the slot 69 seated in the groove 67. The leaf spring 8a is thus connected to the rod 4a and biases the same inwardly to engage the shoulder 7a of the rod 4a against the end wall 6 of the boss, the elongated slot 68 providing for adjustment of the bias.

Mounted upon the free end of the rod 4a is a head 70, preferably formed of plastic, and including the knob or finger piece 10a for effecting manual turning of the rod 4a and an indicia-carrying flange 14a integral with the knob 10a. In this manner, the knob 10 and plate 14 of the previously described embodiment of the invention can be formed in a single moulded piece.

With the sleeve 12 eliminated, the rod 4a is formed with a shoulder 71 against which the head 70 is engaged to position it endwise of the rod 4a. A second shoulder 72 is provided for holding the thread guard 18 against endwise movement on the rod 4a.

In the initial assembly of the tension device according to FIGS. 5 and 6, the rod 4a with the adjusting nut 23 mounted thereon is inserted into the bore 5. The spring 8a is then inserted to hold the rod 4a against endwise movement. The spring 31 is then inserted after which the sleeve 29 and barrel 27 are placed in position and secured by the lever 33. The tension discs 32 and the guard 19 are then positioned on the rod 4a and finally,

6 the head is secured on the end of the rod 4a to lock the assembly. When once assembled in this embodiment, the discs 32 can be removed simply by removing the head 70.

Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to a preferred embodiment of my invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depant from the spirit of the invention are intended to be included within the scope of the appended claim.

Having thus described the nature of the invention, what I claim herein is:

A recessed needle thread tension device for a sewing machine comprising a frame having a hole in the face thereof and bounded by a side wall and an end wall, a rod arranged centrally of said hole and having an inner end portion journaled in said frame in said end wall and having an opposite end portion terminating in a free end, means for securing said rod against endwise movement, a slide member mounted on said rod for endwise sliding, opposed tension discs mounted on said rod outwardly of said slide member, a head removably mounted on the free end of said rod outwardly of said tension discs, means for releasably securing said head to said rod to hold said tension discs on said rod and to provide for turning said rod, spring means disposed within said hole and acting on said slide member to bias said slide member outwardly and thereby bias said tension discs against said head for placing a tension on a thread running between said tension discs, means disposed within said hole and responsive to turning of said rod for varying the comprmsion of said spring means and thereby adjusting the bias on said tension discs, said tension discs being removable ofi the free end of said rod by removal of said head, and means for retracting said slide member from engagement with said tension discs against the action of said spring to release the bias on said tension discs and for holding said slide member in assembled relation on said rod when said head and tension discs are removed.

References Cited in the file of this patent UNITED STATES PATENTS 

